The on-site treatment of a domestic-type waste is used at those locations where there is no access to a municipal water treatment plant or equivalent facility. Examples of such locations are ships and off-shore drilling platforms.
At such locations, the waste typically flows through a biological or fermentation unit on board, and then into a holding tank. When the effluent in the holding tank reaches a certain level, it is pumped through a sterilizing unit where the effluent is sterilized, usually with sodium or calcium hypochlorite. The effluent is then pumped overboard. Such treatment is costly and requires the use of large and heavy, space consuming equipment.